Tells the view that its window object changed.
- iOS 2.0+
- tvOS 9.0+
The default implementation of this method does nothing. Subclasses can override it to perform additional actions whenever the window changes.
window property may be
nil by the time that this method is called, indicating that the receiver does not currently reside in any window. This occurs when the receiver has just been removed from its superview or when the receiver has just been added to a superview that is not attached to a window. Overrides of this method may choose to ignore such cases if they are not of interest.